Detectors indium arsenide

While most other techniques use a limited amount of detectors (e.g., silica for visible, photomultipliers for UV) and MIR has a small number, NIR uses many types of semiconductors for detectors. The original PbS detectors are still one of the largest used in NIR, however, indium gallium arsenide (InGaAs), indium arsenide (InAs), indium antimonide (InSb), and lead selenide (PbSe) are among the semiconductor combinations used, both cooled and ambient. 

Figure 3.15 shows the spectral dependence of the specific detectivity, D, reported for germanium and indium arsenide photodiodes, respectively. The main properties of these detectors are also summarized in Table 3.1 for comparison. 

Typical materials used in NIR photoconductive detectors are PbS, PbSe, InSb and InAs (lead sulphide, lead selenide, indium antimonide and indium arsenide). 

Operating wavelength of the detector should be as close to the cutoff wavelength (Ico = hc/Eg) as possible. This requirement is easiest to meet in three-compound semiconductor materials with continually adjustable bandgap, e.g., mercury cadmium telluride (Hgi- cCd cTe) [8], mercury zinc telluride (Hgi- cZn cTe) [69-71], lead tin telluride Pbi Sn Te [72, 73], and indium arsenide antimonide (Ini - cAS cSb) [74] which for x = 0 reduces to indium antimonide, InSb. 

The detector characteristic may very well be included in the filter design. For example, an indium arsenide photovoltaic detector, operating at 195 K, has a very sharp cut-off at 3.6 m. In combination with a thin germanium window, a well-defined 1.9-3.6 m response function is obtained. However, with a limited number of substances available for the design of filters based on intrinsic absorption and reflection phenomena other methods must be found to constmct filters where the transmission limits can be set by the scientific objectives and not so much by the absorption properties of available substances such methods are based on the interference principle, to be discussed in Section 5.6, but first we deal with prism spectrometers, gas filters, and pressure modulation. 

Instead of glowbars, as used in MIR, tungsten halogen lamps are the sources of light. The detectors are solid-state semiconductors such as lead sulfide (PbS) or indium gallium arsenide (InGaAs). These are orders of magnitude quieter than typical MIR detectors and often more sensitive. 

Indium has many industrial uses for electronics and electrical applications [9] indium metal in germanium transistors indium alloys for soldering and glass sealing of electronic devices indium antimonide, arsenide, and phosphide in infrared detectors and semiconductor applications indium-silver alloys for brazing and electroplated indium metal for electrical connectors. For underground telephone cables, indium has been used to plate copper-to-aluminum connectors. About 2-5 tons of indium alloyed with silver and cadmium has been used annually in nuclear reactor control rods. 

Raman spectroscopy may be performed on either a dispersive instrument or a FT instrument. All of the spectra provided in this chapter were obtained from a FT-Raman instrument (see Fig. 62), featuring a NdiYAG solid-state laser, and a InGaAs (indium-gallium arsenide) detector, combined with a silicon on quartz beam splitter. Note that in the FT-Raman experiment, the sample effectively becomes the source to the FT spectrometer. Dispersive Raman instruments are also popular, and these usually feature a silicon-based array detector (CCD array) in combination with either a visible laser (doubled YAG or HeNe) or a short-wavelength solid-state NIR laser. 

Detector. The radiation is detected by infrared-sensitive semiconductors, such as indium gallium arsenide (InGaAs) or mercury cadmium telluride (HgCdTe, but often abbreviated MCT). Infrared light striking these materials can promote electrons into conduction, allowing the radiation to be detected as an electrical current. 

The material composition of the FPAs determines the detectable IR-spectral frequency range. Many types of detectors are available, ranging from the commonly used indium antimonide (InSb) for near IR and mercury cadmium telluride (HgCdTe, MCT) for the mid IR to the more exotic silicon arsenide (Si As) [10] and uncooled barium strontium titanium (BST) [11]. Mid-IR imaging using MCT FPAs [12] has been the most popular in terms of the number of studies performed, due to its ability to provide access to the molecular-fingerprint region. 

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